Trouble

Oysters are "functionally extinct" in many locations around the globe

to disease and overharvesting, a new study has found.

The wide-ranging survey, published in BioScience, the journal of the

American Institute of Biological Sciences, compares the past and

present condition of oyster reefs around the globe. The international

team of researchers led by Michael Beck of the Nature

the University of California found that more than 90 percent of

former reefs have been lost in most of the "bays" and ecoregions

where the mollusks were formerly abundant.

In many places, such as the Wadden Sea in Europe and Narragansett

Bay, oysters are rated "functionally extinct," with fewer than 1 per- 

cent of former reefs persisting. The declines are in most cases a

result of over-harvesting of wild populations and disease, often

exacerbated by the introduction of non-native species.

"Overall, we estimate that 85% of oyster reefs have been lost

globally," the study says. "Most of the world’s remaining wild

capture of native oysters comes from just five ecoregions in North

America, yet the condition of reefs in these ecoregions is poor at

best, except in the Gulf of Mexico."

Beck's team examined oyster reefs across 144 bays and 44

ecoregions. It also studied historical records as well as

national catch statistics. The BioScience authors rate the

condition of oysters as "poor" overall.

 Oysters provide important ecosystem services, such as filtration,

as well as food for people. The survey team argues for improved

efforts and the removal of incentives to over-exploitation.

It also recommends that harvesting and further reef destruction

should not be allowed wherever oysters are at less than 10 percent

their former abundance, unless it can be shown that these activities

do not substantially affect reef recovery.